The present invention relates to the domain of diagnostics. More precisely, the invention relates to molecular diagnostics of Whipple's disease using detection techniques and/or amplification and sequencing techniques by means of oligonucleotide probes or primers, and their application to research on the presence or identification of bacteria of Tropheryma whippelii type.
Whipple's disease is a disease present in various forms. The most classic form is that of a fever with chronic diarrhoea resulting in loss of weight, but it is also a disease which is susceptible to giving chronic articular attacks, cerebral attacks with dementia, ophthalmologic attacks with uveity and also cardiac arrest, in particular endocarditis with negative haemoculture. Ever since it was described in 1907, Whipple evokes the existence of a bacteria associated with <<intestinal lipodystrophy>> before observation of numerous micro-organisms after silvery coloration of a mesenteric ganglion [Whipple GH (1907) Bull. John Hopkins Hosp. 18: 328]. Bringing to the for of the positive non-specific PAS character (from the English <<periodic acid Schiff>>) of this bacteria, then the observations by electronic microscopy, confirm the presence of an intracellular bacterial species having a positive Gram structure [Chears et al. (1961) Gastroenterology 41:1296]. The universal molecular tool 16S RNAr has helped confirm this hypothesis by specifying the phylogenic taxonomy of this novel bacterial species, and by assigning it the provisional name of Tropheryma whippelii to evoke the notion of intestinal malabsorption and honor the discoverer of the ailment [Reiman D. et al. (1992) N. Engl. J. Med. 327:293]. The direct sequencing of 721 bases of a fragment amplified from a biopsy of the small intestine of a patient [Wilson K H et al. (1991) Lancet 338:474], then from a ganglion of another patient [Wilson K H et al. (1992) ASM News 58:318] confirms the originality of the bacterial species associated with Whipple's disease. The sequencing by Relman et al. (op. cite) of 1321 bases representing 90% of the 16S rDNA gene on a sample, and a fragment of 284 bases in four other patients has helped confirm that the bacterial species associated with Whipple's disease represented a new species, specify its taxonomic position in the phylum of actinomycetes, that is, bacteria having a positive Gram structure with a high content of guanosine plus cytosine, representing a new branching relatively close to two known species in human pathology, Acfinomyces pyogenes and Rothia dentocariosa. 
The rpoB gene codes one of the sub-units of bacterial RNA polymerase and constitutes a genetic marker allowing specific detection of the bacteria of the species Tropheryma whippelii. 
According to Lazcano et al. [J. Mol. Evol. (1988) 27:365–376], the RNA polymerases are divided into two groups according to their origin, with one constituted by the viral RNA- or DNA-dependent RNA polymerases, and the other constituted by the DNA-dependent RNA polymerases of eukaryotic or prokaryotic origin (archaebacteria and eubacteria). The eubacterial DNA-dependent RNA polymerases are characterized by a simple and conserved multimeric constitution known as <<core enzyme>>, represented by αββ′, or <<holoenzyme>> represented by αββ′δ [Yura and Ishihama, Ann. Rev. Genet. (1979) 13:59–97]. Numerous works have brought the functional role to the fore, within the multimeric enzymatic complex, of the β sub-unit of the eubacterial RNA polymerase. The archaebacterial and eukaryotic RNA polymerases present, for their part, a more complex structure of up to ten, even thirty sub-units [Puhlet et al. Proc. Natl. Acad. Sci. USA (1989) 86:4569–4573].
The genes which code the different sub-units αββ′δ of the DNA-dependent RNA polymerase in eubacteria, respectively the rpoA, rpoB, rpoC and rpoD genes, are classed in different groups comprising the genes coding for proteins constituting the ribosomal sub-units or for enzymes implied in the replication and reparation of the genome [Yura and Yshihma, Ann. Rev. Genet. (1979) 13:59–97]. Certain authors have shown that the sequences of the rpoB and rpoC genes could be utilized to construct phylogenetic trees [Rowland et al. Biochem. Soc. Trans. (1992) 21:40S] allowing the different branchings and sub-branchings to be separated among the kingdoms of the living.
Diagnosis of the disease is currently undertaken by observation, after coloration, of microscopic smears obtained from biopsy or by amplification and sequencing of the universal gene tool 16S RNAr (Relman et al., op. cite).
All the same, the 16S gene is a moderately discriminating gene for the identification of the bacteria. In addition, it is necessary to employ several molecular targets for identifying the bacteria, especially to eliminate problems of molecular contamination.
Furthermore, this bacteria was for the first time isolated and cultivated in cellular systems in the laboratory of the inventors [Raoult D. et al. (2000) N. Engl. J. Med. 342:620 and WO 00158440] from the cardiac valve removed from a patient presenting with endocarditis with negative haemoculture (Twist clone).